Lexus SC300 / Lexus SC400. Manual — part 974
128
ECT AND A/T INDICATOR
PO
W
E
R
NO
R
M
A
L
3
4
7
1
5
2
9
1
2
IJ2
3
IK1
5
IK1
2
IK1
22
IJ1
6
IK1
21
IG2
7
1E
12
1K
4
3D
3
3D
6
3B
4
3B
5 3D
3A
4
3D
13
1H
12
B
76
NSW
A
18
P
A
9
2
A
10
L
A
2
SP1
B
17
TT
A
19
TE2
A
28
OD2
IK1
4
IK1
3
I19
A
14
IJ1
10
GR–Y
LG
G–O
G–O
Y
Y
G
W
G–O
GR–R
W–B
Y
Y
Y
ENG
TE1
TT
TE2
ECT
Y
Y
B–
W
B–
W
G–
O
G
W
P
P
P
P
G–
R
G–
Y
GR
–
R
GR
–
R
GR
–
Y
LG
G–
R
G–
Y
GR
–
R
W–
B
G
R
–
R
GR
–
R
G–
O
FROM POWER SOURCE SYSTEM (SEE PAGE 56)
5
7. 5A
ST
10A
GAUGE
ECT PATTERN
SELECT SW
ENGINE AND ECT ECU
O/
D
M
A
IN
SW
TDCL
E 8
E 9
, E1 0
T 6
O5
A
A
10
IH
BR
A
E20
IK1
6
IK1
7
2
2
A
13
A
15
SH
O
R
T
CO
N
NE
CT
O
R
L
–R
L–R
R
3
2
OUT
GND
L–R
R
1
VCC
SPEED SENSOR
NO. 1
S 3
Y
A
B
B
S2
2
A
,S
2
3
129
P
R
N
D
2
1
1
4
6
5
7
8
9
GR
R–
B
L
G–
W
G
W
A/T INDICATOR SW
[NEUTRAL START SW AND
BACK–UP LIGHT SW]
N 1
B
4
C
1
C
2
C
3
C
4
C
5
C
16
A
1
4
10
5
6
7
8
9
I33
I33
I19
I19
I19
I19
I22
I22
IK1
12
IK1
11
IK1
13
IK1
14
IK1
16
IK1
17
C
18
B
A
23
3D
10
3D
9
3H
3
3A
1
1J
1
1E
18
IF
Y
Y
G
W
G–O
GR–R
W–B
W–B
W–B
W–B
GR
–
R
Y
G
W
W
G
G–
W
L
R–
B
GR
G–
O
GR
R–
B
L
G–
W
G
W
Y
GR
R–
B
L
G–
W
G
W
W–
B
W–
B
A/T INDICATOR LIGHT
[COMB. METER]
EC
T
P
O
W
ER
P
R
N
D
2
L
O/
D
OF
F
A/T INDICATOR LIGHT
(FOR SHIFT LEVER)
A21
C12
, C13
, C14 A
W–B
C
P
R
N
D
2
L
W
G
G–W
L
R–B
GR
C
17
3H
1
3A
9
T
O
P
A
NE
L
F
US
E
(US
A
)
TO
IN
TE
G
R
A
TI
O
N
R
E
L
A
Y
(CA
NA
DA
)
1
G–
O
3C
1
G–O
G–O
G–
O
G–
O
G–
O
130
ECT AND A/T INDICATOR
THIS SYSTEM, ELECTRICALLY CONTROLS THE LINE PRESSURE, THROTTLE PRESSURE, LOCK–UP PRESSURE AND ACCUMULATOR
PRESSURE ETC. THROUGH THE SOLENOID VALVE. THE ECT IS A SYSTEM WHICH PRECISELY CONTROLS GEAR SHIFT TIMING AND
LOCK–UP TIMING IN RESPONSE TO THE VEHICLE’S DRIVING CONDITIONS AND THE ENGINE OPERATING CONDITIONS DETECTED
BY VARIOUS SENSORS, MAKING SMOOTH DRIVING POSSIBLE BY SHIFT SELECTION FOR EACH GEAR WHICH IS THE MOST
APPROPRIATE TO THE DRIVING CONDITIONS AT THAT TIME, AND CONTROLS THE ENGINE TORQUE DURING SHIFTING TO ACHIEVE
OPTIMUM SHIFT FEELING.
1. GEAR SHIFT OPERATION
WHEN DRIVING, THE ENGINE WARM UP CONDITION IS INPUT AS A SIGNAL TO TERMINAL (B)44 OF THE ECU FROM THE EFI WATER
TEMP. SENSOR AND THE VEHICLE SPEED SIGNAL FROM SPEED SENSOR NO.2 IS INPUT TO TERMINAL (B)23 OF THE ECU. AT THE
SAME TIME, THE THROTTLE VALVE OPENING SIGNAL FROM THE THROTTLE POSITION SENSOR (MAIN) IS INPUT TO TERMINAL
(B)43 OF THE ECU AS ENGINE RPM CONDITION (IDLING, HIGH LOAD AND ACCELERATION CONDITIONS) SIGNAL.
BASED ON THESE SIGNALS, THE ECU SELECTS THE BEST SHIFT POSITION FOR DRIVING CONDITIONS AND SENDS CURRENT TO
THE ECT SOLENOIDS.
WHEN SHIFTING TO 1ST SPEED, THE CURRENT FLOWS FROM TERMINAL (B)10 OF THE ECU
→
TERMINAL 1 OF ECT SOLENOIDS
→
GROUND AND CONTINUITY TO NO.1 SOLENOID CAUSES THE SHIFT (NO.2 SOLENOID DOES NOT HAVE CONTINUITY AT THIS TIME).
FOR 2ND SPEED, THE CURRENT FLOWS SIMULTANEOUSLY FROM TERMINAL (B)9 OF THE ECU
→
TERMINAL 2 OF ECT SOLENOIDS
→
GROUND, AND FROM TERMINAL (B)10 OF THE ECU
→
TERMINAL 1 OF ECT SOLENOIDS
→
GROUND, AND CONTINUITY TO NO.1
AND NO.2 SOLENOIDS CAUSES THE SHIFT.
FOR 3RD SPEED, THERE IS NO CONTINUITY TO NO.1 SOLENOID, ONLY TO NO.2 SOLENOID, CAUSING THE SHIFT.
SHIFTING INTO THE 4TH SPEED (OVERDRIVE) OCCURS WHEN NO CURRENT FLOWS TO NO.1 AND NO.2 SOLENOIDS. THE NO.4
SOLENOID (FOR ACCUMULATOR BACK PRESSURE MODULATION) IS INSTALLED TO ADJUST THE BACK PRESSURE ON THE
ACCUMULATOR AND CONTROL THE HYDRAULIC PRESSURE DURING SHIFTING AND LOCK–UP IN ORDER TO PROVIDE SMOOTH
SHIFTING WITH LITTLE SHIFT SHOCK.
2. LOCK–UP OPERATION
WHEN THE ECT ECU DECIDES, BASED ON EACH SIGNAL, THAT THE LOCK–UP CONDITION HAS BEEN MET, THE CURRENT FLOWS
FROM
→
TERMINAL (B)8 OF THE ECU
→
TERMINAL 3 OF THE ECT SOLENOID
→
GROUND, CAUSING CONTINUITY TO THE LOCK–UP
SOLENOID AND CAUSING LOCK–UP OPERATION.
3. STOP LIGHT SW CIRCUIT
IF THE BRAKE PEDAL IS DEPRESSED (STOP LIGHT SW ON) WHEN DRIVING IN LOCK–UP CONDITION, A SIGNAL IS INPUT TO
TERMINAL (A)4 OF THE ECU. THE ECU OPERATES AND CUTS THE CURRENT TO THE SOLENOID TO RELEASE LOCK–UP.
4. OVERDRIVE CIRCUIT
* O/D MAIN SW ON
WHEN THE O/D MAIN SW IS TURNED ON (SW POINT IS OPEN), A SIGNAL IS INPUT TO TERMINAL (A)28 OF THE ECU AND THE ECT
CAUSES SHIFT TO OVERDRIVE WHEN THE CONDITIONS FOR OVERDRIVE ARE MET.
* O/D MAIN SW OFF
WHEN THE O/D MAIN SW IS TURNED OFF (SW POINT IS CLOSED), THE CURRENT FLOWING THROUGH THE O/D OFF INDICATOR
LIGHT FLOWS TO GROUND BY WAY OF THE O/D MAIN SW AND CAUSES THE O/D OFF INDICATOR LIGHT TO LIGHT UP. AT THE
SAME TIME, A SIGNAL IS INPUT TO TERMINAL (A)28 OF THE ECU AND THE ECT PREVENTS SHIFT INTO OVERDRIVE.
5. ECT PATTERN SELECT SW CIRCUIT
WHEN THE ECT PATTERN SELECT SW IS CHANGED FROM “NORMAL” TO “POWER”, THE CURRENT THROUGH THE GAUGE FUSE
FLOWS TO TERMINAL 4 OF ECT PATTERN SELECT SW
→
TERMINAL 3
→
TERMINAL (B)4 OF A/T INDICATOR
→
TERMINAL (C)23
→
GROUND AND CAUSES THE INDICATOR LIGHT TO LIGHT UP. AT THE SAME TIME, THE CURRENT FLOWS TO TERMINAL (A)18 OF
THE ECU AND THE ECU PERFORMS SHIFT UP AND SHIFT DOWN AT A HIGHER VEHICLE SPEED RANGE COMPARED WITH
“NORMAL” POSITION.
6. KICK DOWN OPERATION
WHEN THE ACCELERATOR IS DEPRESSED FURTHER THAN THE FULL THROTTLE POSITION WHILE DRIVING, THE KICK DOWN SW
TURNS ON AND ITS SIGNAL IS INPUT TO TERMINAL (A)3 OF THE ECU. THEN, THE ECU CONTROLS THE CURRENT WHICH FLOWS
FROM TERMINALS (B)10 AND (B)9 OF THE ECU TO THE NO. 1 AND NO. 2 SOLENOIDS AND SHIFTS DOWN BY TURNING THE
SOLENOIDS ON AND OFF.
7. CRUISE CONTROL
WHEN CRUISE CONTROL OPERATION IS SELECTED A SIGNAL IS INPUT TO TERMINAL (A)12 OF THE ECU FROM CRUISE CONTROL
ECU. AS A RESULT, THE ECU OPERATES AND CONTROLS OVERDRIVE, LOCK–UP AND SO ON FOR SMOOTH DRIVING.
SYSTEM OUTLINE
131
E 1
ECT SOLENOID
1–4 : APPROX. 5.3
2–5 : APPROX. 3.7
3–GROUND : APPROX. 13.2
6–GROUND : APPROX. 13.2
E 2
EFI WATER TEMP. SENSOR
1–2 : APPROX. 16.2K
(–20
°
C –4
°
F)
APPROX. 2.5K
(20
°
C 68
°
F)
APPROX. 0.32K
(80
°
C 176
°
F)
E 8
ECT PATTERN SELECT SW
4–3 : CLOSED WITH ECT PATTERN SELECT SW AT POWER POSITION
E 9
(A),
E10
(B) ENGINE AND ECT ECU
BATT – E1:
ALWAYS APPROX. 12 VOLTS
IGSW – E1:
APPROX. 12 VOLTS WITH IGNITION SW ON
BK
– E1:
APPROX. 12 VOLTS WITH BRAKE PEDAL DEPRESSED
P
– E1:
APPROX. 12 VOLTS WITH IGNITION SW ON POSITION AND ECT PATTERN SELECT SW AT POWER POSITION
KD–GROUND :CONTINUITY WITH KICK DOWN SW ON
OD2
– E1:
APPROX. 12 VOLTS WITH O/D MAIN SW ON
0 VOLTS WITH O/D MAIN SW ON
+B–GROUND
: APPROX. 12 VOLTS WITH IGNITION SW AT ON POSITION
+B1–GROUND : APPROX. 12 VOLTS WITH IGNITION SW AT ON POSITION
MREL–GROUND:APPROX. 12 VOLTS WITH IGNITION SW AT ON POSITION
E01–GROUND : ALWAYS CONTINUITY
E02–GROUND : ALWAYS CONTINUITY
L–GROUND
: APPROX. 12 VOLTS WITH SHIFT LEVER AT “L” RANGE
2–GROUND
: APPROX. 12 VOLTS WITH SHIFT LEVER AT “2” RANGE
R–GROUND
: APPROX. 12 VOLTS WITH SHIFT LEVER AT “R” RANGE
E1–GROUND
: ALWAYS CONTINUITY
VC–VTA1
: LESS THAN 1 VOLTS WITH THROTTLE VALVE FULLY CLOSED
MORE THAN 3 VOLTS WITH THROTTLE VALVE OPEN
VTA1 – E2:
CONTINUITY WITH THROTTLE VALVE FULLY CLOSED
APPROX. 4K
WITH THROTTLE VALVE FULLY OPEN
VC
– E2:
APPROX. 5 VOLTS
O 1
O/D DIRECT CLUTCH SPEED SENSOR
1–2 : APPROX. 620
S 4
SPEED SENSOR NO.2 (FOR ECT)
1–2 : APPROX. 620
S12
STOP LIGHT SW
2–1 : CLOSED WITH BRAKE PEDAL DEPRESSED
SERVICE HINTS
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